www.nature.com/scientificreports
OPEN
Received: 12 January 2018 Accepted: 12 April 2018 Published: xx xx xxxx
Prenatal alcohol exposure increases the susceptibility to develop aggressive prolactinomas in the pituitary gland Shaima Jabbar1,2, Kenneth Reuhl3 & Dipak K. Sarkar1,3 Excess alcohol use is known to promote development of aggressive tumors in various tissues in human patients, but the cause of alcohol promotion of tumor aggressiveness is not clearly understood. We used an animals model of fetal alcohol exposure that is known to promote tumor development and determined if alcohol programs the pituitary to acquire aggressive prolactin-secreting tumors. Our results show that pituitaries of fetal alcohol-exposed rats produced increased levels of intra-pituitary aromatase protein and plasma estrogen, enhanced pituitary tissue growth, and upon estrogen challenge developed prolactin-secreting tumors (prolactinomas) that were hemorrhagic and often penetrated into the surrounding tissue. Pituitary tumors of fetal alcohol-exposed rats produced higher levels of hemorrhage-associated genes and proteins and multipotency genes and proteins. Cells of pituitary tumor of fetal alcohol exposed rat grew into tumor spheres in ultra-low attachment plate, expressed multipotency genes, formed an increased number of colonies, showed enhanced cell migration, and induced solid tumors following inoculation in immunodeficient mice. These data suggest that fetal alcohol exposure programs the pituitary to develop aggressive prolactinoma after estrogen treatment possibly due to increase in stem cell niche within the tumor microenvironment. The National Cancer Institute has established that alcoholic beverage is a human teratogen and human carcinogen1. Moreover, International Association of Research on Cancer’s 2009 survey identify that around 3.5% of cancer deaths in USA are caused by alcohol consumption2,3. A number of reports have now demonstrated that alcohol abuse promotes development of aggressive tumors of breast, prostate, pancreas, and colon tissues in human patients4–6. The cause of alcohol promotion of tumor aggressiveness is not clearly understood, but recent evidence suggests that enhanced estrogen signaling might be involved in alcohol promotion of tumor aggressiveness. Using an animal model of fetal alcohol exposure, Hilakivi-Clarke and colleagues have shown elevated plasma estrogen levels may increase the risk for mammary tumor development in fetal alcohol exposed offspring7. Polanco and colleagues have also connected increased plasma estrogen levels with the tumor promotion in fetal alcohol exposed rats8,9. The ovarian steroid estradiol is also known to increase pituitary prolactin (PRL)-producing lactotropic cell proliferation and to induce prolactinoma development in humans as well as in laboratory animals10–14. Prolactinomas account for approximately 40% of all pituitary tumors and are an important cause of hypogonadism and infertility in human15,16. While most are benign and can be controlled by current therapies, some show a lack of sensitivity to a combination therapies or recur during follow-up and are considered as aggressive with unclear epidemiology17. Whether environmental imprinting may influence the development of aggressive prolactinomas has not been studied. We therefore determined if fetal alcohol exposure, which causes stable alcohol epigenetic marks on the genome18–20, promotes development of aggressive prolactinomas using a Fischer-344 (F344) rat animal model.
1
The Endocrine Program, Department of Animal Sciences, Rutgers, The State University of New Jersey, 67 Poultry Lane, New Brunswick, NJ, 08901, USA. 2Endocrinology and Animal Biosciences Graduate Program, Rutgers, The State University of New Jersey, 84 Lipman Drive, New Brunswick, NJ, 08901, USA. 3The Environmental and Occupational Health Sciences Institute, Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 140, Frelinghuysen Road, Piscataway, NJ, 08854, USA. Correspondence and requests for materials should be addressed to D.K.S. (email:
[email protected])
ScIEnTIfIc REPortS | (2018) 8:7720 | DOI:10.1038/s41598-018-25785-y
1
www.nature.com/scientificreports/
Results
Fetal alcohol exposure increases pituitary weights and levels of pituitary prolactin (PRL), plasma PRL, pituitary aromatase, pituitary ESR1 and plasma estrogen in female offspring. In
the first study, we evaluated if fetal alcohol exposure increased pituitary and systemic levels of estrogen and alters lactotrope functions by measuring the pituitary content of PRL and aromatase protein levels using immunohistochemical procedures. We also measured aromatase and alpha estrogen receptor mRNA levels in these tissues using quantitative RT-PCR methods. Additionally, we measured plasma levels of PRL and estrogen by ELISA assays and also determined pituitary weight differences between fetal alcohol-fed and control-fed rats. As expected from our previous work21, pituitary PRL immunoreactivity was increased in fetal alcohol-fed (AF) animals (Fig. 1A,B). Immunohistochemical staining data also showed increased numbers of aromatase-stained cells in AF animals’ pituitary tissues (Fig. 1C,D). We found that Prl mRNA and aromatase mRNA levels, but not estrogen receptor 1 (Esr1) mRNA levels, were elevated in AF offspring as compared to control-fed (AD and PF) offspring (Fig. 1E–G). Additionally, we found that plasma estrogen levels (Fig. 1H), plasma PRL levels (Fig. 1I) and pituitary weights (Fig. 1J) were higher in AF animals as compared to controls. These data suggest that in utero alcohol exposure enhances the production of plasma and pituitary estrogen and PRL levels and the pituitary weight during the adult period in the offspring.
Fetal alcohol exposure increases the development of prolactinomas with aggressive behavioral phenotypes in the pituitary after estrogen treatment in adult female rats. Because estrogen is
mitogenic to lactotropes12–14, we hypothesized that prolonged elevation of estrogen production, particularly in the pituitary, in fetal alcohol exposed offspring may lead to the development of pituitary tumors. To address this, we first compared the effects of estrogen on pituitary weight and plasma PRL in fetal alcohol exposed and control diet-exposed offspring. These data are shown in Fig. 2. As demonstrated in this figure, estrogen-treatment via a silastic capsule known to maintain plasma estrogen levels about 150 pg/ml for a period of three months22, increased both pituitary weights (Fig. 2A) and plasma levels of PRL (Fig. 2B). Inspection of the pituitary gland 120 days after estrogen treatment revealed that some of the tumors in pituitaries of AF animals were highly vascularized and penetrated to the sphenoid bone (Fig. 2C; top two panels). Pituitaries of estrogen-treated AD and PF rats were smaller, less vascularized and were situated within the sphenoid bone (Fig. 2C; bottom two panels). Histopathological inspections showed that pituitaries of AF animals were composed of small round tumor cells in a solid pattern, densely granulated and strongly acidophilic (indicator of rare prolactinomas), with necrotic regions, the epithelial cells colonized in nested shape surrounded with blood vessels (indicators of angiogenesis signaling) (Fig. 2D; top two panels. The pituitary tumor section from AD and PF animals, in contrast, showed uniform, weakly acidophilic epithelial cells with infiltration of eosinophilic cells (Fig. 2D; bottom two panels). These data provide both anatomical and histopathological evidence for the development of aggressive type pituitary prolactin secreting tumors in fetal alcohol-exposed female rats following estrogen treatment.
Fetal alcohol exposure increases expression of biomarkers for pituitary tumor aggressiveness. As noted earlier, pituitary tumors are generally adenomas but some may show aggressive and/or malig-
nant behaviors23. Several biochemical markers (Ki67, P53, FGFR4, PTTG, MMP9) are used to identify the tumor aggressiveness in clinics24. By employing immunohistochemical methods we determined the changes in these biochemical marker proteins in pituitaries of fetal alcohol-fed (AF) and control-fed (AD and PF) rats. As shown in Fig. 3A,B, KI67 immuno-labelled cell number was higher in the pituitary of AF rat than those in the pituitary of AD and PF controls. Similarly, the number of P53 immuno-labelled cells was elevated in the pituitary of AF rats (Fig. 3C,D). The protein and mRNA levels of oncogenes (FGFR4, PTTG and MMP9) in the pituitaries were also determined. Fetal alcohol exposed pituitaries showed increased protein (Fig. 3E,F) and gene expression levels of FGFR4 (Fig. 3G) as compared to control rat pituitaries. Fetal alcohol-exposed pituitaries also showed increased protein and mRNA levels of PTTG (Fig. 3H–J) and MMP9 (Fig. 3K–M). These biochemical data are in agreement with those histopathological data shown in Fig. 2 and support the view that pituitaries of fetal alcohol exposed rats develop aggressive tumors following estrogen treatment.
Fetal alcohol exposure increases expression of stem-like cells in the pituitary tumors. Recently, pituitary stem cells (PSCs) have been proposed to play a role in pituitary tumorigenesis, particularly in the formation of aggressive pituitary tumors25,26. To determine if pituitary tumors of fetal alcohol-exposed rats contains PSCs, we measured stem cell marker proteins SOX2, CD133 and OCT4 by immunocytochemistry and their precursor genes by q-PCR in the tumor tissues. As shown in Fig. 4, SOX2, CD133 and OCT4 immuno-labelled cell numbers were higher in pituitaries of fetal alcohol-exposed rats than those in pituitaries of control rats (Fig. 4A,B,D,E,G,H). Fetal alcohol-exposed pituitaries also showed increased mRNA levels of Sox2 (Fig. 4C), Cd133 (Fig. 4E) and Oct4 (Fig. 4H) compared to control rat pituitaries. These data suggest that the tumors in the pituitary of fetal alcohol-exposed rats contain more stem-like cells than those in pituitaries of control rats. When pituitary tumor cells of AF-treated and control (AD)-treated rats were grown in ultra-low attachment plates, a large number of spheres developed from AF pituitary tumor cells while a small number of spheres developed from AD pituitary tumor cells (Fig. 5A). AF pituitary tumor cell spheres (tumorispheres) grew rapidly and at a six-fold higher rate than that in AD pituitary tumorispheres (Fig. 5B). AF tumorispheres expressed higher levels of stem cell marker (Oct4, Nanog, Klf4, Sox2, Cd133, Cd44, Nestin, and Cd34) mRNAs (Fig. 5C) and most of their protein counterparts (Fig. 5D). These results indicate that pituitary tumors of AF rats have expanded stem cell niche. Pituitary tumorisphere cells of fetal alcohol exposed rat show increased tumorigenicity. Colony formation assay is one of the in vitro techniques that examine the ability of the cells to form colonies in semisolid
ScIEnTIfIc REPortS | (2018) 8:7720 | DOI:10.1038/s41598-018-25785-y
2
www.nature.com/scientificreports/
Figure 1. Effects of fetal alcohol exposure on pituitary prolactin (PRL) content (A,B) and aromatase content (C,D) as determined by immunocytochemical detection, pituitary Prl mRNA level (E), aromatase mRNA level (F), plasma estrogen level (G), pituitary estrogen receptor 1 (Esr1) mRNA level (H) plasma PRL (I) and pituitary weight (J) in female rats. Alcohol-fed (AF), pair-fed (PF) and ad libitum-fed (AD) rat offspring were used during the adult period (90 days) on the day of estrus. Data are mean ± SEM (n = 6–8) and were analyzed using one-way analysis of variance (ANOVA) with the Newman-Keul posthoc test. *p
